The invention relates to an arrangement for feeding a liquid additive from a receptacle into a fuel line or into an exhaust pipe of an internal-combustion engine of a motor vehicle by way of a blockable feed line leading into at least one of the above-mentioned lines and by way of a pump which at least temporarily generates a feed pressure in the feed line, the receptacle being fillable with additive from a larger storage tank also accommodated in the motor vehicle by way of a blockable connection line.
In the case of internal-combustion engines, particularly in the case of Diesel engines, it is known to feed an additive to the fuel or to the exhaust gas, which additive contributes to the emission control. Such an additive can, for example, lower the ignition temperatures for soot particles for their burning and can be used for soot filter cleaning in the exhaust system. German patent document DE 102 29 483 A1 describes this state of the art. For a more precise apportioning of the additive, an additive pre-volume is formed here in a receptacle separate from the additive tank. This additive pre-volume is fed in an apportioned manner to the fuel line by use of a sucking jet pump.
It is an object of the invention to construct an arrangement for feeding a liquid additive from a receptacle into a fuel line or into an exhaust pipe of an internal-combustion engine such that an operation is ensured under all operating conditions that has as few problems and is as reliable as possible, and the structure of the arrangement is uncomplicated.
According to the invention, an arrangement is provided for feeding a liquid additive from a receptacle into a fuel line or into an exhaust pipe of an internal-combustion engine of a motor vehicle by way of a blockable feed line leading into at least one of the above-mentioned lines and by way of a pump, which at least temporarily generates a feed pressure in the feed line. The receptacle is fillable with additive from a larger storage tank also accommodated in the motor vehicle by way of a connection line that can be blocked. The feeding line branches-off the connection line between the receptacle and the storage tank. The pump is installed in the receptacle or between the receptacle and the branching-off of the feed line into the connection line. The connection line can be shut-off in the storage tank or between the storage tank and the branching-off of the feed line.
This has the advantage that the feed line as well as the receptacle can be charged from the storage tank by way of the connection line by use of the pump. The connection line, acting as a flow pipe, leads from the receptacle to the storage tank and can be connected there, for example, by way of a T-joint, to a solenoid valve, as a further shut-off valve, and to the feed line. The filling of the receptacle from the storage tank takes place, for example, in the control device overrun. For this purpose, the delivery direction of the pump is reversed and the solenoid valve at the storage tank is opened while the feed line is closed by the injection valve. When the level sensor detects that the receptacle is filled, the solenoid valve will be closed and the injection valve will be opened in order to evacuate the line by suction.
In the case of this advantageous embodiment of the invention, the delivery direction of the pump can be reversed. This also simplifies the construction of the arrangement. In this case, by way of a control device, the functions of, on the one hand, the feeding of additive from the receptacle by way of the injection valve into the fuel line or the exhaust pipe of the internal-combustion engine and, on the other hand, the filling of the receptacle from the storage tank can advantageously be controlled by changing the rotating direction of the pump.
Another advantageous embodiment of the invention provides that the blockable lines can be shut-off by use of shut-off valves, particularly solenoid valves. Likewise in a manner controlled by the control device, it thereby becomes easily possible to open or close the lines required for the respective operating situation.
A preferred embodiment of the invention provides that a blockable return line into the receptacle branches off the connection line or the feed line between the pump and the shut-off valves. Together with a heating device in the receptacle for heating at least a partial volume of the additive, a lasting heating concept is thereby implemented, which is necessary because, for example, a 32.5% urea solution as the additive would freeze at approximately minus 11 degrees centigrade. In the receptacle with a provided volume of from 5 to 8 liters, the heating element will first melt a kind of cavity-type hole into the frozen urea solution. As soon as sufficient molten additive will then be available, warm additive can be delivered by way of the pump via the return line onto the surface of the frozen additive in the receptacle, which additive will thereby begin melting at its upper surface. For this reason, it is advantageous for the connection line to end in the proximity of the heating device, particularly in the bottom area of the receptacle and, for the return line to end at the top in the receptacle. Thus, by way of the return line and the receptacle, an additive circulation can take place, which assists the heating element during the thawing of the additive.
Further preferred embodiments of the invention provide that the receptacle, as well as the storage tank, has at least one closable, in particular, manually closable and/or self-closing, refill opening. As a result, different approaches advantageously remain possible for carrying out the required filling tasks. Mainly when the, in particular, self-closing refill opening is constructed as a coupling device for the connection with a filling device, the construction of the arrangement described in the following may be achieved.
The storage tank for the additive is not accommodated in the engine compartment, but rather in a luggage compartment, cargo space or under the trunk, (such as in place of or in a spare wheel well), and cannot be heated. It has a volume of between 16 and 35 liters in order to, in each case, have to be refilled only in the servicing interval when visiting the shop. It therefore has a self-closing refill opening constructed as a coupling device for a filling device. Thus, a stationary filling by way of a refueling hose advantageously becomes possible, where the additive is fed in a manner closed off from the environment. A suction device, a level measuring or switch-off device, and additional devices may be used, similar to the state of the art of refueling systems for fuels. When the motor vehicle is in use, the driver usually does not have to pay any attention to the storage tank or it does not manifest itself to the driver.
In contrast, the receptacle for the additive is accommodated in the engine compartment and is connected with the storage tank by way of the connection line. It has a refill opening which is to be operated manually and has a screw cap. Such a customer-suitable filling possibility of the receptacle, which receptacle is relatively small in comparison with the storage tank, is simple, can be provided without changing the body shell and is necessary, for example, in the event that the additive in the storage tank freezes and the receptacle can therefore no longer be filled from the storage tank by way of the pump. In this case, a level measuring device for the additive present in the receptacle indicates that a refilling of the receptacle, for example, by the driver, is appropriate. The risk of a system failure at low temperatures will thereby advantageously be minimized.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.